This invention relates to die casting and clamp type machines and more particularly to the method and apparatus for removing a tie bar from the machine by captively removing the tie bar nut by power means. By use of the machine functions and auxiliary tie bar gripping means, a tie bar can be removed from the front plate of the machine so that a mold or die can be removed or inserted into the die casting machine.
In the die casting industry, the tie bar nuts hold the tie bars and the machine platens in rigid alignment when the die is closed and molten metal is shot into the mold cavity. These bars are normally a simple threaded device with machined surfaces on the nut which abut the die casting machine platens. The machines tie bars are under high tension when closed during the shooting of metal into the die cavity to prevent flashing on the part. At this time these tie bars and nuts sustain the full impact of the shot in conjunction with the pre-load stress that is put on the bars of the machine when the machine is closed and locked up. The maximum clamp tonnage or size of a given machine will obviously determine the size of the tie bars and the nuts that are utilized therein. On small machines, the removal of these tie bars and nuts can be done manually without a great deal of difficulty.
When a die is to be inserted or removed from a die casting machine, or for that matter, any type of clamp operated machinery utilizing tie bars, it is sometimes necessary because of the size of the mold itself to remove one or more of the tie bars so that the mold can be removed from the machine. For the small size die casting machines, that is, machines in the range of 450 to 750 ton capacities, the removal of these nuts is done manually by service personnel. However, in larger size die casting machines, such as 850 to 1,500 ton units, it becomes necessary to use nut hangers as a safety device because of the weight of those nuts. The problem is even more accute in units of 3,000 ton capacity and extreme caution must be used. These tie bar nuts weigh approximately 350 pounds each and therefore, it is difficult to unthread, hold and remove the nut from the tie bar. Further, the physical size of the tie bar in a 3,000 ton machine for example is approximately 14 inches in diameter and the nut 22 inches across. The removal of this tie bar and nut from the machine therefore becomes a complicated and difficult task.
In my invention, a geared member has been fastened to the outside periphery of the tie bar nut by a key means. This gear member is then driven by a second gear in mesh with it via a worm gearing mechanism connected to a hydraulic motor. This mechanism allows the tie bar nut, therefore, to be rotated by this power drive means to remove the nut from the tie bar itself. Means are provided to hold the nut captive to the platen of the machine while the nut is rotated which literally will push the tie bar out of the machine when the nut is rotated.
Such mechanisms using gearing are not new. British Pat. No. 707,988, shows a manual system whereby the coupling and decoupling of pipe ends can be accomplished using threaded members which have external gearing associated with them. A similar gearing mechanism is shown in U.S. Pat. No. 2,541,772 which shows a gearing means associated with die stripping plates for removing the stripper plate nut which is inconveniently located in such a mechanism. The U.S. Pat. No. 3,289,282 entitled Apparatus For Dismantling and Assembling Roll Assemblies shows an automatic means for removing threaded members from roll assemblies wherein a drive coupling engages with a geared member associated with the roll coupling and is automatically rotated to remove the threaded coupling from the roll assembly. U.S. Pat. No. 4,092,881 titled Apparatus For Making Up and Breaking Threaded Pipe Connections shows a system whereby a chuck can be released and clamped about threaded tubular members. A cylinder is energized which rotates and breaks the coupling between the pipe connections. This is cited since a similar actuator mechanism is used in the process of my invention.